Gun blast diffuser



y 14, 1979 R. H. MEADOWS ET AL 3,520,226

arm BLAST DIFFUSER Filed July 12, 1968 2 Sheets-Sheet 1 INVENTORS ROBERT H. MEADOWS RONALD E. VOL KER ATTORNEYS July 14, 19?0 MEADQWS ET AL 3,520,226

GUN BLAST DIFFUSER 2 Sheets-Sheet 2 Filed July 12, 1968 INVENTORS ROBERT H. ME'A DOWS RONALD E. VOL KER ATTORNEYS United States Patent 3,520,226 GUN BLAST DIFFUSER Robert H. Meadows, Edmundson, and Ronald E. Volker,

St. Charles County, Mo., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed July 12, 1968, Ser. No. 744,469 Int. Cl. F41f 17/12 US. Cl. 89-14 1 Claim ABSTRACT OF THE DISCLOSURE An apparatus for diffusing and directing the energy from a gun blast including a shroud surrounding one or more gun barrels with said shroud being a resonant chamber for rebounding energy from a first gun blast at an angle against energy of a succeeding gun blast whereby the energy of the succeeding gun blast is diffused and deflected.

BACKGROUND OF THE INVENTION The present invention relates to an auxiliary device for automatic weapons, such as a machine gun, and more particularly relates to an auxiliary device for preventing damaging shock waves from causing engine flame out and protecting fragile equipment on an aircraft from the shock produced by firing a weapon, such as a rapid firing cannon. The device includes a resonant chamber which is tuned so that energy from a preceding gun blast will rebound at the same time the next blast occurs so that the rebound energy will diffuse and force downward the succeeding blast.

The use of auxiliary devices attached to or adjacent to gun barrels is quite old in the gun art. For example, the idea that a baffle just outside the muzzle could be used to provide a thrust to reduce the recoil momentum dates back prior to World War I. These devices which are referred to as muzzle brakes, have had widespread use, particularly during World War II on antitank guns. Heretofore, however, there has not been any need to diffuse or direct a gun blast in any particular direction. Most present day military aircraft, such as the McDonnell Douglas Corporation Phantom II, has a radome in the forward fuselage and a Gatling type cannon is positioned in the forward fuselage beneath the radar. The repeated shock waves created by firing the weapon can have an adverse effect on the relatively frangible hardware of the radar system. Accordingly, it is desirable to reduce as much as possible, this adverse effect caused by repeated and rapid firing of the weapon.

Also gun installations located forward of jet engine inlet ducts frequently cause engine operational problems such as compressor stall or engine flame out when the weapon is fired at moderate to high altitudes (35,000 to 50,000 feet and above). The engine problems are re lated to interruption of the air flow due to pressure and/ or temperature changes to normal air inlet flow of the engine due to muzzle blast eflects. The diffusion and deflection of muzzle blast and residue from engine inlets can improve or prevent the detrimental engine operational effects caused by firing the weapon. The diversion and diffusion of muzzle blast away from the engine air inlet ducts is therefore also a desired result of any muzzle diffuser located forward of the engine inlets on a high performance jet aircraft.

SUMMARY OF THE INVENTION The present invention relates to a gun blast diffuser which is a cylindrical shroud that is attached to an aircraft fuselage. A slanted cutoff is provided on the outerice extending end thereby forming a short longitudinal length and a long longitudinal length with intermediate lengths joining the short and long lengths. A resonant chamber is provided and is formed by a portion of the shroud and a forward plate and a rear gas sealing plate. The size of the resonant chamber is such that a previous blast will rebound at the same time a next succeeding blast will occur.

It is therefore a general object of the present invention to provide an apparatus for diffusing and deflecting the gun blast from an airplane mounted weapon.

Other objects and advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a sectional view taken on line 44 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1 and 2 of the drawings, a forward end of an airplane fuselage 11 is shown having a radome 12. A gun 13, such as a multi-barrel machine gun, is mounted to the fuselage and a shroud 14 surrounds the barrels of the gun.

As best shown in FIGS. 2 and 4 of the drawings, the unattached or free end of shroud 14 is cut off at a slant with the upper surface 15 nearest the radome having the longest length and the lower surface 16 which is approximately degrees from the upper surface being the shortest length. A resonant chamber 17 is provided inside shroud 14 and is formed by the arcuate surface of shroud 14, plate 19 and rear gas sealing plate 21. A change in diameter of chamber 17 has little effect on tuning, however, the length of the chamber is important in tuning. In this respect, the frequency is similar to that of vibration in closed organ pipes. See, for example, the text, Classical and Modern Physics, by Harvey E. White, D. Van Nostrand Co., Inc., pages 200203, for a discussion of standing waves in resonating air columns.

In operation, energy from a first gun blast enters into chamber 17 and then rebounds or exits through the aperture below gun 13. The dimensions of chamber 17 are such that the energy entering into chamber 17 will exit at a time when the next succeeding blast occurs. Accordingly, the succeeding gun blast is diffused and deflected downwardly away from radome 12. In flight the forward plate 18 is designed to utilize the ram air to further aid in deflecting the gun blast downwardly and away from the radome. Enery is stored in chamber 17 in the form of a traveling wave and at the time of a second blast the wave will have rebounded back to the location of the gun muzzle where it will help deflect the second blast downward. The wave will also absorb some of the energy from a second blast which will cause the wave to rebound again, thereby repeating the cycle and the second blast will help dissipate some of the energy of the third blast, and so on. By way of example, a gun blast diffuser embodying the present invention has been employed on a military aircraft which fires a 20 mm. shell at a rate of 6,000 rounds per minute.

It can thus be seen that the present invention pro- 3 4 vides a relatively inexpensive and simple device for tudinal shroud portion thereby partially closing said protecting a radorne on an aircraft from shock waves forward opening, and caused by a rapidly firing weapon. It also diffuses and a rear gas sealing plate closing the aft end of said deflects the muzzle blast away from the engine inlet cylindrical shroud, the length of said cylindrical ducts. Obviously many modifications and variations of shroud between said fiat plate and said rear gas the present invention are possible in the light of the above 5 sealing plate being such that a resonant chamber teachings. isformed whereby energy from a preceding gun We claim: blast is rebounded to diffuse and deflect energy from 1. A resonant chamber tuned for dilfusing and directa succeeding gun blast. ing energy from a gun blast of a gun comprising: 10

a cylindrical shroud surrounding the muzzle of said References Cited gun, said shroud having a forward opening formed FOREIGN PATENTS by a slanted forward edge extending beyond the end of said muzzle of said gun whereby said slanted forward edge provides a long longitudinal shroud 5 portion and a short longitudinal shroud portion,

a flat plate attached within said cylindrical shroud at said long longitudinal shroud portion and extend- BENJAMIN ABoRcHELTPnmary Exammer ing angularly downward away from said short longi- S. C. BENTLEY, Assistant Examiner 1,469,523 1/1967 France.

811,236 4/ 1959 Great Britain. 814,895 6/ 1959 Great Britain. 

